Background and Data Sources

In 2020 and 2021, the Census Bureau released several data products meant to demonstrate the effect of the Bureau’s new Disclosure Avoidance System (DAS) on population counts (using 2010 census data). The final demonstration product using the same privacy parameters applied to the 2020 census data was released in June 2021. The University of Minnesota’s IPUMS National Historical Geographic Information System (NHGIS) volunteered to convert the Census Bureau’s un-tabulated demonstration data into useful summary formats, linked to the published 2010 summary data. The intent of both organizations was for census data users to use these tabulated files to assess the impact of the DAS on their own local data. NHGIS tabulated data is located here. Information on the DAS is located here.


Total Municipality Population

The mean absolute change in population between the published 2010 data and the demonstration product data is -0.3 people. The largest absolute change in population between the two files is for Chicago with an increase of 31 people in the demonstration data. The mean percent change in population for all Cook County towns is 0.007%. There are 0 towns with a percent change in total population of more than 5%. The town with the largest percent change in the demonstration total population counts is Bedford Park with a percent change of 0.52%. These patterns are reflected in the box plots below.


Conclusions: Total municipality populations are unlikely to be largely impacted by the 2020 DAS parameters and can be used without reservation.




Hispanic/Latino Municipality Population

The mean absolute change in the Hispanic/Latino population by municipality between the published 2010 data and the demonstration product data is -0.12 people. The largest absolute change in population between the two files is for Chicago with a decrease of 197 people in the demonstration data. The mean percent change in the Hispanic/Latino population for all Cook County towns is -0.48%. There are 13 towns with a percent change in the Hispanic/Latino population of more than 5%. The town with the largest percent change in the demonstration Hispanic/Latino population counts is Robbins with a percent change of -28.6%. The median percent change is 0% and the interquartile range is [-1.04%, 0.82%]. The number of outliers and IQR varies by public health district.


Conclusions: When aggregated, the variation introduced by the DAS settings for the Hispanic population at the municipal level largely balances out. This means we can be reasonably confident in the 2020 jurisdiction-level Hispanic/Latino population estimate, as calculated by the subtraction method. However, at the individual municipality level, while the majority of towns are within acceptable bounds for percent change, outliers do exist - some with very high levels of distortion. Outliers are more prevalent in areas where the Hispanic/Latino population is low. Calculation of rates for the Hispanic/Latino population at the municipal level should be avoided for the North and South District and must be accompanied by data caveats if performed. Alternatively, a minimum population threshold of 500 or 1000 could be applied, below which rates would be censored.


Towns with >5% Change in Hispanic/Latino
Municipality Published Total Published H/L Demonstration H/L Percent Change
Robbins 5337 175 125 -28.57
Phoenix 1964 116 102 -12.07
Barrington Hills 4209 114 102 -10.53
Matteson 19009 813 749 -7.87
Kenilworth 2513 41 38 -7.32
Deer Park 3200 110 102 -7.27
Ford Heights 2763 42 39 -7.14
South Barrington 4565 118 110 -6.78
Lincolnwood 12590 859 810 -5.70
Richton Park 13646 477 501 5.03
Winnetka 12187 271 291 7.38
Northfield 5420 159 171 7.55
Inverness 7399 178 197 10.67




Non-Hispanic Black Municipality Population

The mean absolute change in the non-Hispanic Black or African American population by municipality between the published 2010 data and the demonstration product data is 2.8 people. The largest absolute change in population between the two files is for Chicago with an increase of 90 people in the demonstration data. The mean percent change in the non-Hispanic Black population for all Cook County towns is -1.38%. There are 25 towns with a percent change in the non-Hispanic Black population of more than 5%. The town with the largest percent change in the demonstration population data is Forest View with a percent change of -40%. The median percent change is 0% and the interquartile range is [-1.58%, 0.47%]. The number of outliers and IQR varies by public health district.


Conclusions: When aggregated, the variation introduced by the DAS settings for the non-Hispanic Black population at the municipal level, though larger than for the Hispanic population, largely balances out. This means we can be reasonably confident in the 2020 jurisdiction-level non-Hispanic Black population estimate, as calculated by the subtraction method. However, at the individual municipality level, close to 1 in 5 towns have percent changes in population outside acceptable bounds. As expected, outliers are more common in areas where the non-Hispanic Black population is low. Calculation of rates for the non-Hispanic Black population at the municipal level should be advised against for towns outside of the South District. When rates must be calculated, strong data caveats should be included. Alternatively, a minimum population threshold of 500 or 1000 could be applied, below which rates would be censored.


Towns with >5% Change in non-Hispanic Black Population
Municipality Published Total Published NHB Demonstration NHB Percent Change
Forest View 698 5 3 -40.00
Golf 500 3 2 -33.33
Bedford Park 580 4 3 -25.00
Palos Park 4847 36 29 -19.44
Winnetka 12187 31 25 -19.35
Harwood Heights 8612 53 44 -16.98
Hodgkins 1897 6 5 -16.67
Riverwoods 3660 26 22 -15.38
Lincolnwood 12590 129 111 -13.95
Inverness 7399 36 31 -13.89
Park Ridge 37480 168 145 -13.69
Hometown 4349 38 34 -10.53
Lemont 16000 58 53 -8.62
Deerfield 18225 93 85 -8.60
Northfield 5420 26 24 -7.69
Riverside 8875 110 103 -6.36
Palos Heights 12515 208 197 -5.29
Countryside 5895 179 189 5.59
Franklin Park 18333 167 178 6.59
Willow Springs 5524 56 61 8.93
Western Springs 12975 43 48 11.63
Deer Park 3200 28 32 14.29
Kenilworth 2513 7 8 14.29
Barrington 10327 96 110 14.58
Barrington Hills 4209 32 40 25.00




Non-Hispanic Asian Municipality Population

The mean absolute change in the non-Hispanic Asian population by municipality between the published 2010 data and the demonstration product data is 0.23 people. The largest absolute change in population between the two files is for Skokie with an increase of 60 people in the demonstration data. The mean percent change in the non-Hispanic Asian population for all Cook County towns is 1.59%. There are 33 towns with a percent change in the non-Hispanic Asian population of more than 5%. The town with the largest percent change in the non-Hispanic Asian demonstration data is Hodgkins with a percent change of 100%. The median percent change is 0% and the interquartile range is [-1.77%, 1.12%]. The number of outliers and IQR varies by public health district.


Conclusions: When aggregated, the variation introduced by the DAS settings for the non-Hispanic Asian population at the municipal level, though larger than for the Hispanic population, largely balances out. This means we can be reasonably confident in the 2020 jurisdiction-level non-Hispanic Asian population estimate, as calculated by the subtraction method. However, at the individual municipality level, over 20% of towns have percent changes in population outside acceptable bounds. Outliers are present in all public health districts but distortions are particularly high in the South. Calculation of rates for the non-Hispanic Asian population at the municipal level should be avoided whenever possible. When rates must be calculated, strong data caveats should be included. Alternatively, a minimum population threshold of 500 or 1000 could be applied, below which rates would be censored.


Towns with >5% Change in non-Hispanic Asian Population
Municipality Published Total Published NHA Demonstration NHA Percent Change
Calumet Park 7835 24 3 -87.50
Barrington Hills 4209 272 239 -12.13
East Dundee 2860 76 68 -10.53
Posen 5987 20 18 -10.00
Crestwood 10950 105 95 -9.52
Steger 9570 96 87 -9.38
Dolton 23153 68 62 -8.82
Riverside 8875 184 168 -8.70
Hometown 4349 14 13 -7.14
Golf 500 15 14 -6.67
Hazel Crest 14100 91 85 -6.59
Calumet City 37042 108 101 -6.48
Kenilworth 2513 33 31 -6.06
Deer Park 3200 136 128 -5.88
Countryside 5895 86 81 -5.81
Western Springs 12975 179 170 -5.03
North Riverside 6672 137 144 5.11
Matteson 19009 187 197 5.35
Park Forest 21975 157 167 6.37
Country Club Hills 16541 162 174 7.41
Blue Island 23706 79 85 7.59
Chicago Heights 30276 87 95 9.20
Glenwood 8969 27 30 11.11
Palos Park 4847 82 94 14.63
Riverdale 13549 13 15 15.38
Merrionette Park 1900 19 22 15.79
Thornton 2338 16 19 18.75
Burnham 4206 21 27 28.57
South Chicago Heights 4139 46 61 32.61
Forest View 698 13 19 46.15
Dixmoor 3644 2 3 50.00
Ford Heights 2763 3 5 66.67
Hodgkins 1897 2 4 100.00




District Population Estimates

Based on the analyses above, individual municipalities may have race and ethnicity population estimates with significant distortion, but these distortions balance each other out when municipalities are aggregated to create jurisdiction level population estimates. CCDPH public health districts are also aggregations of municipalities. The table below displays the percent change in each type of population estimate at the district level.


Conclusions: When aggregated, the variation introduced by the DAS settings balances out for both total and all racial/ethnic population estimates. District-level population estimates can be used without reservation.


Percent Change in Population Estimates by District
District Total Hispanic Non-Hispanic Black Non-Hispanic Asian
North 0% -0.03% 0.21% 0.01%
South 0% -0.06% 0.11% 1.26%
Southwest -0.01% 0.22% -0.25% -0.23%
West 0% 0.01% -0.03% -0.31%